The present invention deals with environmental concerns which are increasingly being expressed with respect to supermarket refrigeration systems. One of these concerns is the amount of energy being consumed to provide refrigeration and air-conditioning in such establishments. A further concern is with the amount and types of refrigerants currently being used. Present supermarket refrigeration systems typically employ very large quantities of chlorinated fluorocarbon refrigerants such as R502 which, when released into the atmosphere, are highly destructive of the ozone layer. While less environmentally damaging refrigerants are available, such as R22, these refrigerants are not well adapted to cooling cycles spanning large temperature differentials, such as those processes normally utilized in maintaining frozen foods.
Among the objects of the present invention may be noted the provision of an integrated multi-temperature refrigeration system; the provision of such a system which provides energy efficient operation; the provision of such a system in which the refrigerant thermal cycles span relatively small temperature differentials; the provision of such a system which can utilize environmentally preferable refrigerants; the provision of such a system which requires a relatively small refrigerant charge; the provision of such a system which is particularly adapted for use in a supermarket environment; the provision of such a system which facilitates the process of defrosting of evaporators employed in food freezers; the provision of such a system which is highly reliable and which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.